New fat, same old problem with an added twist?

Last month, New York City outlawed the use of partially hydrogenated oils, known as trans fats, in restaurants, a ban now under consideration in other cities, including Boston and Chicago. But novel research conducted in Malaysia and at Brandeis University shows that a new method of modifying fat in commercial products to replace unhealthy trans fats raises blood glucose and depresses insulin in humans, common precursors to diabetes. Furthermore, like trans fat, it still adversely depressed the beneficial HDL-cholesterol.

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Published online in Nutrition and Metabolism the study demonstrates that an interesterified fat - (a modified fat that includes hydrogenation followed by rearrangements of fats molecules by the process called interesterification) enriched with saturated stearic acid - adversely affected human metabolism of lipoproteins and glucose, compared to an unmodified, natural saturated fat. Interesterification to generate a stearic acid-rich fat is fast becoming the method of choice to modify fats in foods that require a longer shelf life because this process hardens fat similar to oils containing trans-fatty acids. The new study shows that interesterification, which unnaturally rearranges the position of individual fatty acids on the fat molecule, can alter metabolism in humans.

"One of the most interesting aspects of these findings is the implication that our time-honored focus on fat saturation may tell only part of the story," explained biologist and nutritionist K.C. Hayes, who collaborated on the research with Dr. Kalyana Sundram, nutrition director for palm oil research at the Malaysian Palm Oil Board in Kuala Lampur.

"Now it appears that the actual structure of the individual fat molecule is critical, that is, the specific location of individual fatty acids, particularly saturated fatty acids, on the glycerol molecule as consumed seems to make a difference on downstream metabolism of fat and glucose," said Hayes. Both Hayes and Sundram are experts on human lipid metabolism and were instrumental in the development of Smart Balance